Starting unit, more particularly for internal-combustion engines, and method of operating same



Dec. 15, 1953 A. L. VlNTENON 2,662,986

STARTING UNIT, MORE PARTICULARLY FOR INTERNAL-COMBUSTION ENGINES, AND

METHOD OF OPERATING SAME Filed July 8, 1952 M wil //V 1 15 N 7 0/? ANDRE A 00/5 l///V7'E/VOA/ Patented Dec. 15, 1953 UNITED STATES iih t'l'ENT OFFICE STARTING UNIT, MORE PARTICULARLY FOR INTERNAL-COMBUSTIGN ENGINES, AND METHOD OF OPERATING SAME Andr Louis Vintenon, Bois-Colombes, France, assignor to Electrom, Neuilly-sur-Seine, Seine,

France, a company 8 Claims.

The electrical starting or turbo-jet engines, in particular, is effected by an electric motor which, when in operation for starting, is mechanically connected to the rotor of the gas turbine engine through a suitable reducing gear. Electric current is supplied to said electric motor from a storage battery or other constant voltage source through a set or" contactors and resistances so that the current flow is conveniently con-- trolled. The number of starting stages is generally no more than two or three in order to provide a relatively light and simple equipment. The passage from one stage to the next produces current peaks in the starting motor circuit, which may reach or exceed three times the final running intensity, and therefore the full power may not be increased by means of a higher voltage, which would result in undesirable high current intensities. As a further drawback besides tr e resulting heating, such current peaks cause troubles in the starting motor commutation and fatigue of the battery and/or the starting unit.

The power absorbed by the started engine, more particularly in the case of a gas turbine, increases rapidly as the speed of revolution of said started engine increases; therefore, for a quick start, the starting motor should reach as high a power as possible, which can be achieved only by increasing the voltage in the last stage of the starting operation. If the known starting rheostat devices were to be used, the number of starting stages should be considerably increased, as is the practice in electric traction for example, which would however result in unduly complicated and heavy equipment with a very low efficiency causing imperfect utilization of the power of the batteries and starting units.

The object of the present invention is to elin inate such a drawback by feeding the starter of an internal combustion engine in such a way that a constant intensity electric current is supplied under a voltage which increases from a determined minimum value during the starting period.

In a particular embodiment of a device to carry out the above specified current feeding method, the starting unit comprises an internal combustion starting engine mechanically connected to a starting electric generator the field coil 01" which is fed by the armature by being connected in parallel therewith, the branch circuit of the field coil comprising in series a regulator of the type comprising a pile of carbon discs, said pile being pressed or released by an electromagnetic member the circuit of which is con- 2 trolled by pilot regulators of the vibrating contact type.

Said constant current generator, the voltage of which increases from a minimum value, is preferably associated with a time-op rat d circuitbreaker adapted to cut oil the starter from its current supply after predetermined interval of time.

In order that the invention may be more clearly understood and readily carried into practiee, it will now be described more fully and illustrated, by way of example only, in he accompanying diagram, which shows the various elements or a constant current, variable tension starting unit and their connections.

The installation comprises an internal COli'lbLlS-= tion starting engine 1 mechanically connected to drive a starting electric generator 2, the armature of which is connected in series with a coil 3 for compound excitation. The shunt field coil :3 of generator 2 is connected to one pole thereof directly and to the other pole through a pile 3 of carbon discs. Said. pile 5 is pressed or released by the armature 8 of a solenoid the coil 3 of which is in series with a calibrating multiple tap resistor 8 in a circuit connected in parallel with said generator 2.

The calibrating resistor 8 has two tappings for feeding voltage and intensity pilot vibrator switches. Tapping t is connected to lead to which includes a switch blade ll. At a point between tapping S and switch is is connected the vibrating member [2 of the basic voltage pilot regulator 13. Beyond switch it, lead nected to the vibrating member it tensity pilot regulator E5.

The stationary contact it of regulator 53 is connected to one end of the continuous oscillation keep-up coil ita whereof the other end is connected to a lead ii. The stationary contact i 5a of the intensity pilot regulator is conected to one end of a continuous oscillation esp-up coil 5b the other end of which is co nected to a lead I 8. Lead ii and lead it 30. into lead is which is connected to the outlet lead 29 of generator 2.

The tapping H of calibrating resistor 8 is connected through a lead 22 to the vibrating member 23 of a final voltage pilot regulator the stationary contact 24a of which is connected to one end of the continuous oscillation keep-up coil 24b the other end of which is connected through lead 25 to main lead 19.

Regulator it includes a compensating coil one end of which is connected to lead through a basic voltage adjustment rheostat 25. The other end of coil I31) is connected to the stationary contact 21 of a break relay 28 the movable blade 29 of which is connected through lead 39 to the second. outlet lead 3! of generator 2. The coil 28a of relay 28 is connected in series in lead 3!.

The intensity pilot regulator is provided with a compensating coil l5c which also is connected in series in lead 3 i.

The final voltage pilot regulator 2c is provided with a compensating coil Zdc one end of which is connected to lead 2i! through a final voltage adjustment rheostat 32, the other end of coil 250 being connected through a lead 33 to lead 3 which connects together coils 28a and [50.

Lead 35 connects the other end of coil i'eic to a hand-operated isolating switch 36 from which a lead 3! leads to the stationary contact BBaof the main starting contactor 38. Beyond main contactor 38 is inserted the shunt-39 of anindicating ammeter ll], after which the current passes through lead ll to feed the series type starter d2 of the internal combustion engine to be started, which starter is connected on the other side to lead 2t through a lead 43.

The coil 38b of the main contactor 38 is connected by a lead id to one stationary contact d5 of a starting push-button switch the other-stationary contact st of which is connected through lead Ail to lead 3?. Coil 382) may also be fed through the movable armature aim of a holding relay it, the stationary contacts 5%, 5! of which are connected in parallel with contacts d5, it. The coil 4% of the holding relay C 9 is connected between contact 5i and a lead 52 which, through a contactor 53 the opening of which is operated by an adjustable clockwork 5 3, is connected to the return lead 55 connecting coil 38b to lead 29.

The clockwork and the holding relay may be made inoperative by a three-way switch 56 the movable blade of which is adapted to connect lead M and contact d5 either to contact 5l, or to an intermediary shunt circuit 51 comprising a hand-operated break switch 58. Contact 5! is also connected to one end of a coil 59 adapted to initiate the clockwork operationthe otherend of which is connected to lead 56. An indicating voltmeter $6 is connected between leads 3! and 55.

The above described equipment operates as follows:

When the starting engine l is running, starting generator 2 rotates. With isolator 36 closed,

and switch 55 off bridge 5'! and closed to holding relay coil 59b, if the push-button which connects contacts id and i6 is depressed, then the'current issued from generator 2, under basic voltage, will excite the holding relay coil 582), the coil 59 which initiates the clockwork operation and the coil 38b of the main starting relay 38. The basic voltage pilot regulator 53 operates to maintain the conditionsior the generation of an electric current under a voltage lower than the .fin'al voltage, which, while suflicient to permit the operating relays to be instantaneously .actuated, will keep down to a safe value the intensity of the current absorbed by the starter 52 the circuit of which is completed immediately relay 3%.; operates.

As soon as the contactor of relaySB closes,'the flow of current causes relay 28 to break and almost immediately thereafter pilot regulator i3 ceases to operate while the intensitypilotregu- .lator l5 becomes operative alone.

Said pilot regulator i5 periodically short-circuits, at a suitable frequency, the part of calibrating resistor 8 comprised between lead 28 and tapping 9, and the current passing through solenoid i so controls the compression of carbon pile 5 that the field coil t of the generator is fed with such a current that the current supplied to starter 52 is maintained to a constant value. The characteristic of starter 42 being of the series type, the arrangement is self-regulating since, as the speed of starter 42 is allowed to increase, the counter-electromotive force of said starter armature may also rise, so that the volt age may rise precisely in relation to the more or less rapid acceleration of the starter 22, which is connected to the internal combustion engine,

not shown, tobe started. During acceleration,

the increase of motor :32 counter-electromotive force would cause the intensity to drop but for the action of regulator l5 on pile 5 to maintain a constant intensity.

As a constant value of the intensity-is maintained, the voltage will not rise above vthe maxinium value assigned to the starting installation by the calibration of .rheostat 32. When the voltage reaches said maximum value-the final voltage regulator-.2 2 becomes operative and fixes a limit to the compression of carbon pile-5 by periodically short-circuiting, at the suitable frequency, the part or" resistor s comprised between tapping 2i and lead 26. .After'the final voltage has been reached, thestarting operation may continue with a decreasing current intensity.

In practice, however, clockwork 5t breaks contact 53 and cuts :off the current from holding coil 49, so that main contactor 33 opens.

Such a starting arrangement may in practice be applied to any existing starters. The suitable constant current value can be determined by the sole condition that the heat losses be the same as in the case or" a constant voltage supply. As most of the losses are caused by Joule effect in the starter windings, the constant intensity which will produce the sameheat losses'by Joule effect as the variableintensity of the constant voltage supply in the same total time is easily calculated by integrating the heat 'functiondeduced from the curve of said variable intensity plotted against time. In the practical case of a starter for modern aircraft turbo-jet engines, said constant current is about 740 amperes-when the final voltage is limitedto 28 volts, which is the standard voltage actually. The final power obtained is 20.7 kilowatts, which is nearly double the power that can be attained when constant voltage starting is used. "Such increased power does not prejudice the starter, the heating of which is the same, if not evenless. The starter has an easier operation due to elimination of high current peaks. As the power increases progressively, damages to the starter collector and to the movable members of the connections are avoided. Furthermore, the operating time for the starter is reduced since the speed increases more rapidly and consequently the ignition of the jet engine is more quickly obtained. The starter heating limitations could actually be made still wider and the constant current could be chosen greater than specified above, the starting time being further reduced accordingly.

Itmay be noted that the operation of sucha starting unit is adapted tosuit various .condi tions of utilization, according'to the quicker for slower acceleration of the started engineindifferent temperature or altitude conditions. The

F cut on" t nt voltage current irrespective of the current now. Furthermore, by changing the position of switch clockwork is made inoperative,

enerator S: is made to operate to supply acon-- main contactor it then being closed either by depressing the push-button which connects contacts in which case the main contactor will only be closed while the push-button is held, or through switch 58 which directly controls the inain contactor and allows to keep it steadily closed.

Of course, without depart ng from the scope of the invention, modifications may be made to above described embodiment.

l cl "nethoo. for supplying the electric current electrical starter of an internal combustion the, more particularly for turbo-jet engine, by means of a starting generator driven by a engine, comprising, in succession, the steps of controlling before starting the tension of the current supplied by the generator to have a constant tension equal to the necessary tension value at the beginning or" the starting operation, then, when the starting operation begins, of controlling the current supplied by the generator to have a constant intensity equal to that necessary for performing the starting operation while the tension of said supplied current increases, and, when said tension attains the value of the final tension for the startfng operation, of controlling the tension of the supplied current to said final value.

2. A method :for supplying the electric current to the electrical starter of an internal combustion engine, more particularly for turbo-jet engine, means of a starting generator driven by a sta ting engine, said starter having a series winding, comprising, in succession, the steps of controlling before starting the tension of the current supplied by the generator to have a constant tension equal to the necessary tension value at the beginning of the starting operation, then, when the star ing operation begins, of controlling the current supplied by the generator to have a constant intensity equal to that necessary for performing the starting operation while the tension of said supplied current increases, and, when the counter-electroinotive force or the starter attains a value equal to that of the final tension for the starting operation, or" controlling the tension of supplied current to said final value.

A starting unit for internal combustion engines, more particularly for turbo-jet engines, c rnprising, in combination, a starting engine, a ,tarting generator connected with said starting ngine, an electrical starter supplied by said genrator, means for maintaining before the starting the tension of the current supplied by the starting generator to the value necessary for the be- "heostat the unit constituted by engine i end ginning of the starting operation, means for elim inating said maintaining means at the beginning of the starting operation, means for maintaining at the beginning during the performing of the starting operation the current supplied by said generator to a constant starting operation, means for maintaining at the end of the starting operation the increasing tension of the current supplied by said generator to the starter at a value equal to the final tension necessary for said starting operation, when the then increasing tension attains said final value, and means for automatically cutting the upplying of said starter after a predetermined time.

comprising, in co'nbination, a eta-rung engine, a starting generator connected with said starting engine and having a shunt field coil, an electrical starter having a series winding, main leads connecting said starter with said starting generator, an adjustable regulator connected in series with said shunt coil, a device for modifying the adjustment of said regulator, a voltage pilot regulator co ected with said device and acting for maintaining the tension of the cur'ent supplied by the generator to the necessary value at the beginning of the starting operation, an intensity pilot regulator connected with said device for maintaining the current supplied by the to constant intensity equal to that necessary for lg the starting operation, for s'ibstitu said. intensity pilot regulator for voltage pilot regulator at the beginning of the starting operation, a second voltage pilot regulator connected with said device for maintaining the tension of the supplied current to the value of the final tension for the star ing operation when the co er-eiectromotive force of said starter attains value of said -final tension, 9, main contactor inserted in one or" said main l ads, means for closing said main contactor begin of the start-i1 g operation, means for maintaining said contactor in closed position during the starting operation, for opening said contactor after a predetermined time, and means for avoiding at will the action of said maintaining and opening means on said main contactor.

5. A starting unit for interna co:

starting engine and having a s generator connected with said st lllt starter having a se necting said starter 5, g an adjustable regulator connected in series with said shunt field coil having a pil of carbon discs, a comp *ession releasto act on said. discs, and a solen of which is connected r .1 s

connecting solenoid in loBrlZLlbi in n erator, a calibrating mounte tor connected with one or" tial voltage pilot re ulator, and an regulator, said in. -,l volt and regulators being connected pa second tapping; means substitu tensity pilot regulator to said voltage pilot regulator at the beginning of the s ...ting operation; a main contactor insert in one or" said main leads, means for closing said main contactor at the beginning or the starting operation,

means for rnaintaining said contactor in closed position duringtheistarting operation; means for opening said contactor afterza predetermined time, and means for avoiding at will the action of said maintaining and opening'means on said main contactor.

6. Aistarting unit for internal combustion engines, more particularly for turboejet engines, comprising, in cornbinatioma.startingengine, a starting generator connectedwith said starting engine and having a shunt'fieldicoil, an electrical starter having a series winding, mainle'ads connecting said starter with said starting; generator; an adjustable regulator connected in series with said shunt field coil and having aipilenf carbon discs, a compression and release device adapted to act on said discs, and a solenoid the"armature of which is connected with said device; aeircuit connecting said solenoid in parallel with the generator, a calibrating resistor mountedin series in said circuit, two tappings displaceable along said calibrating resistor; :a final "voltage pilot regulator of the vibratingicontacttype connected with one of to "gator Inaintaining'the tension of the supplied current to the value of the final tension for the starting operation'when the counterelectroinotive forc'elof said starter attains the va c of said finaltension, the vibrating contact of saidfinal voltage pilot regulatorsshortoircuiting the part of the calibrating resistor comprised beyondsaiditapping; an initialvoltage pilot regulator of the vibrating contact type for maintaining the tension oi' he current supplied by the generator to the necessary value at the beginning of the starting operation, an intensity pilotregulator of the vibrating contact type for maintaining the Lcurrent supplied by the generator to a constant intensity equal to that necessary to 1 performing the starting operation, said initial voltage and intensity pilot regulators connected in parallel with the second tapping, the vibrating contacts or said both regulators short-circuiting the part or" the calibrating resistor comprised beyond said second tapping; means for sn tituting said intensity pilot regulator to said initial voltage pilotzregulator' at the beginning of the starting operation; a main contactor inserted in one ofv said leads, means for closing said main contactor at the beginning of the starting operation, means for maintaining said contactcr inclcs-ed position duringthe startin; operation, means ioropenin said contactor after a predetermined time, and nieans'foravoiding at will the action of said maintaining and opening means on said main. contactor.

7. A starting unit for internal combustioniengines, particularly for turbo jet engines comprising, in combination, a starting en'gina a starting generator connected with said starting engine having ashunt field coil, an electrical starter having a series winding, main leads connecting said starter with said starting generator; an adjustable regulator connected inseries with said shunt field coil and having a p ileof "carbon discs, a compression and release device adapted to act on said discs, and a solenoid the armature oi which is connected with said device; ialcircuit connecting said solenoid in parallel with the generator, a calibrating resistor mounted in series in said circuit, two tappings displaceable along said calibrating resistor; a final voltage pilot'regulator of the vibrating contact type connected wit one of said tappings for maintaining the tension of the supplied current to the value of the final tension for the starting operation when the counter-'electromotiye.force of said starter attainsthe value of saidifinal'tension, the vibrating contact of said final voltage pilot regulator shortcircuiting the part of the calibrating resistor comprised beyond said tapping, said final voltage pilot regulator having a compensating coil, a circuit connecting compensating coil in parallel with the generator, and adjusting rheostat inserted in said circuit; an initial voltage'pilot regulator'oi the vibrating contact having'a compensating coil mounted in series in one of the main leadsior maintaining the tension of the current supplied by the generator to the necessary value at the beginning of the starting operation; an intensity pilot regulator or" the vicrating contact typeior' maintaining the current supplied by the generator to a constant intensity equal to that'necessary for performing the starting operation, said initial voltage and intensity pilot regulators being connected in parallelwith the second tapping, vibrating contacts of said both regulators shoitcircuiting the part of the calibrating resistor comprised beyond said second tapping said ini al voltage pilot regulator having acornpensa ng coil, connecting said last compensating coil in parallel with the generator, an adjusting .rheostat inserted in said last circuit, a niovableicontact inserted in said last circuit, andan operating coil connected in series in one or main leads for opening said movable contact in inediately the current is supplied to the starting motor; a main contactor ined in one of said leads, means for closing said. main coiltactor at the beginning of the starting operation, means for ma ntaining said contactcr in closed position during the starting operation, means for opening said, ccntactor after a predetermined time, and means for avoiding at will the action of maintaining and opening means on said main'contactor.

3. A starting unit, ecording to claim 2, Wherein the means for closing, maintaining and open ing the main contactor an 1 the means for avoiding the action of ma and opening means comprise a main cell for operating the main contact-or mounted in parallel between the main leads, a star ing pushbutton mounted in series with said main coil, a holding relay connected with said main coil, an adjustable electrically actuated clockwork having a ccntactor inserted in series between the coil of the holding relay and said coil and an operating coil mounted in parallel between the coil of said holding relay and said main coil, athree-ivay switch mounted in series between the coil or the holding relay and said main coil, an intermediary shunt circuit connecting one of the contacts of said three-way switch with the line connecting the holdin -relay with one of the main leads and a hand-operated break switch inserts series in said intermediary shuntcircult.

ANDRE- LOUIS VINTENON.

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